C++ StringBuilder::characters16方法代码示例

// This is only needed for TextDocuments where we might have text nodes
// approaching the default length limit (~64k) and we don't want to
// break a text node in the middle of a combining character.
static unsigned findBreakIndexBetween(const StringBuilder& string, unsigned currentPosition, unsigned proposedBreakIndex)
{
    ASSERT(currentPosition < proposedBreakIndex);
    ASSERT(proposedBreakIndex <= string.length());
    // The end of the string is always a valid break.
    if (proposedBreakIndex == string.length())
        return proposedBreakIndex;

    // Latin-1 does not have breakable boundaries. If we ever moved to a differnet 8-bit encoding this could be wrong.
    if (string.is8Bit())
        return proposedBreakIndex;

    const UChar* breakSearchCharacters = string.characters16() + currentPosition;
    // We need at least two characters look-ahead to account for UTF-16 surrogates, but can't search off the end of the buffer!
    unsigned breakSearchLength = std::min(proposedBreakIndex - currentPosition + 2, string.length() - currentPosition);
    NonSharedCharacterBreakIterator it(breakSearchCharacters, breakSearchLength);

    if (it.isBreak(proposedBreakIndex - currentPosition))
        return proposedBreakIndex;

    int adjustedBreakIndexInSubstring = it.preceding(proposedBreakIndex - currentPosition);
    if (adjustedBreakIndexInSubstring > 0)
        return currentPosition + adjustedBreakIndexInSubstring;
    // We failed to find a breakable point, let the caller figure out what to do.
    return 0;
}

static bool parseHTMLIntegerInternal(const CharacterType* position, const CharacterType* end, int& value)
{
    // Step 3
    int sign = 1;

    // Step 4
    while (position < end) {
        if (!isHTMLSpace<CharacterType>(*position))
            break;
        ++position;
    }

    // Step 5
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 6
    if (*position == '-') {
        sign = -1;
        ++position;
    } else if (*position == '+')
        ++position;
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 7
    if (!isASCIIDigit(*position))
        return false;

    // Step 8
    StringBuilder digits;
    while (position < end) {
        if (!isASCIIDigit(*position))
            break;
        digits.append(*position++);
    }

    // Step 9
    bool ok;
    if (digits.is8Bit())
        value = sign * charactersToIntStrict(digits.characters8(), digits.length(), &ok);
    else
        value = sign * charactersToIntStrict(digits.characters16(), digits.length(), &ok);
    return ok;
}

static bool parseHTMLNonNegativeIntegerInternal(const CharacterType* position, const CharacterType* end, unsigned& value)
{
    // Step 3
    while (position < end) {
        if (!isHTMLSpace(*position))
            break;
        ++position;
    }

    // Step 4
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 5
    if (*position == '+')
        ++position;

    // Step 6
    if (position == end)
        return false;
    ASSERT(position < end);

    // Step 7
    if (!isASCIIDigit(*position))
        return false;

    // Step 8
    StringBuilder digits;
    while (position < end) {
        if (!isASCIIDigit(*position))
            break;
        digits.append(*position++);
    }

    // Step 9
    bool ok;
    if (digits.is8Bit())
        value = charactersToUIntStrict(digits.characters8(), digits.length(), &ok);
    else
        value = charactersToUIntStrict(digits.characters16(), digits.length(), &ok);
    return ok;
}

static bool parseFontSize(const CharacterType* characters, unsigned length, int& size)
{

    // Step 1
    // Step 2
    const CharacterType* position = characters;
    const CharacterType* end = characters + length;

    // Step 3
    while (position < end) {
        if (!isHTMLSpace(*position))
            break;
        ++position;
    }

    // Step 4
    if (position == end)
        return false;
    ASSERT_WITH_SECURITY_IMPLICATION(position < end);

    // Step 5
    enum {
        RelativePlus,
        RelativeMinus,
        Absolute
    } mode;

    switch (*position) {
    case '+':
        mode = RelativePlus;
        ++position;
        break;
    case '-':
        mode = RelativeMinus;
        ++position;
        break;
    default:
        mode = Absolute;
        break;
    }

    // Step 6
    StringBuilder digits;
    digits.reserveCapacity(16);
    while (position < end) {
        if (!isASCIIDigit(*position))
            break;
        digits.append(*position++);
    }

    // Step 7
    if (digits.isEmpty())
        return false;

    // Step 8
    int value;

    if (digits.is8Bit())
        value = charactersToIntStrict(digits.characters8(), digits.length());
    else
        value = charactersToIntStrict(digits.characters16(), digits.length());

    // Step 9
    if (mode == RelativePlus)
        value += 3;
    else if (mode == RelativeMinus)
        value = 3 - value;

    // Step 10
    if (value > 7)
        value = 7;

    // Step 11
    if (value < 1)
        value = 1;

    size = value;
    return true;
}